Air inlet construction



Nov. 1, 1960 P. e. DOOLEY AIR INLET CONSTRUCTION Filed Feb. 25, 1959 INVENTOR. E: /P @0045) 2,958,195 Am INLET CONSTRUCTION Philip G. Dooley, Bolton, Conn, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Feb. 25, 1959, Ser. No. 795,571

2 Claims. ((31. 6039.69)

This invention relates to air inlet constructions and more particularly to an improved form of air inlet construction or scoop means for supplying air to the combustion chamber of a gas turbine engine or the like.

One object of the invention is to improve the mixing of fuel and air in a combustion chamber to thereby improve the efiiciency of the combustion therein. 7

Another object of the inventionis to direct air into a combustion chamber in a direction substantially tangential to the exit diameter of the fuel nozzle associated therewith.

Another object of the invention is to inject air into a combustion chamber in counter-rotating streams.

Another object of the invention is to provide an air inlet construction which produces a divergent vortex flow pattern in a combustion chamber.

In conformity with these objects, the preferred embodiment of the invention is characterized by a combustion chamber having a scoop-like means mounted on the front end thereof for collecting and discharging air into the combustion chamber in the region contiguous to the fuel injection nozzle. The scoop-like means assumes the form of a series of individual scoop or bowl-shaped members which are arranged in a stacked or nested relationship and which are separated or spaced a prededetermined distance apart by a plurality of vane elements. Air entering the scoop members and striking the vane elements is introduced into the combustion chamber in counter-rotating streams and the stacked construction of the scoop members creates a diverging vortex fiow pattern.

These and other objects of the invention will readily become apparent to those skilled in the art from an ex- 2; and

Fig. 4 is another end elevation of the preferred embodiment of the air inlet construction or scoop means viewed from the discharge or outlet end thereof.

Referring more particularly to Fig. 1, there is shown a combustion unit for a. gas turbine engine or the like including an air shroud or housing 10 in which is carried an inner casing member or housing 12 defining a combustion chamber. Housing member 10 and combustion chamber 12 are both substantially circular in cross-section (not shown) and are held in assembled engagement by a bracket assembly 14 including a circular plate or ring member 16 carried by pairs of brackets 1818 and 20-20 which are attached or secured to the housing 10 and combustion chamber 12, respectively.

Any suitable means (not shown) such as rivets or welding may be employed to hold the components of the bracket assembly 14 in assembled engagement and also to rigidly connect the bracket assembly 14 to both the housing 10 and combustion chamber 12. Moreover, more than one bracket assembly may be utilized if necessary to maintain the assembly and structural rigidity of the housing 10 and combustion chamber 12.

One end ofhousing 10 is reduced in diameter at 22 and is connected to the combustion chamber outer wall at 24 to thereby provide an air jacket or air space 26 between the housing 10 and combustion chamber 12. The opposite end of the housing 141 is sealed with an end Wall 28, and the end wall 28 carries a plurality of inlet conduits 30 (only two shown) for admitting air into jacket space 26, the air being supplied through conduits 30 to support combustion in combustion chamber 12 as willbe discussed more in detail hereinafter.

Combustion chamber 12 is provided with an outlet or exhaust aperture 32 at one end thereof and at the opposite end thereof is defined by a substantially frustoconical body portion 34 which in effect provides the combustion chamber with a divergent inner wall or inlet surface 36.

Air is supplied to the frusto-conical body portion. 34 of the combustion chamber by the scoop means or air inlet construction of the present invention generally designated by the reference numeral 38. In this particular instance, the scoop means 38 takes the form of a plurality of. individual scoop members or scoop elements, four in'number, which are constructed as a unit and are attached to the end wall of the frusto-conical portion 34 of the combustion chamber at 40', the specific structural detail s of the, scoop means 38 and the function thereof to be discussed more fully hereinafter in connection with Figs. 12, 3 and 4. Suflice it to say at this point, however, thatthe plurality of scoop elements comprising the scoop means .38 are arranged substantially concentrically with theoutermost scoop element being connected to the combustion chamber at 40 by any suitable means such as welding or brazing.

42in this instance is attached or fixed to the housing end wall 28 by any suitable means (not shown) and extends substantially longitudinally of the housing In to a point where it firmly engages innermost scoop member of the scoopmeans 38. It will be appreciated, however, that the-nozzle 42 could be supported in an alternative manner in that it could be rigidly connected to the. scoop means. This preferred construction, it will be understood, is merely exemplary of the invention and is not to be construed in a limiting sense. Nozzle 42 ispro'vided with an orifice 44 therein in the front wall thereof and the exit diameter of the orifice 44 is defined by a beveled or diverging wall 48. A fuel line or fuel conduit 50 communicates with the nozzle '42 and connects the nozzle with a source of fuel (not shown).

Referring to Figs. 2, 3 and 4, the scoop means 38 is shown in this instance as comprised of four dished or substantially bowl-shaped members or scoop elements 52, 54, 56 and 58, member 52 representing the outermost scoop element and member 58 representing the innermost scoopelement. The scoop elements are arranged in a stacked or nested relationship and are spaced apart a predetermined distance and held in assembled engagement by a plurality of'vane elements 60, 62, 64 and 66. The scope elements or scoop members 52, 54, 56 and 58 are substantially circular in configuration, as best seen in Figs. [and 4,:and inassembly- (Fig. 3) are arranged such that T" a e the end walls 68, 70, 72 and 74 thereof defining the inlet end of the scoop means lie in a common plane and such that the end walls 7 6, 78, 80 and 82 defining the outlet end of the scoop means are stepped or progressively increased indiameter.

The Vane element 50, 62, 64, and 66 (Fig. 2) are spaced substantially equidistantly around the peripheries of the four scoop members and are attached or secured thereto by any suitable means such as brazing or Welding, the fillets or connecting means being deliberately omitted from the drawings in order to preserve the clarity of the structural details thereof. Each vane element is adapted to closely follow or engage the peripheral surface of the two scoop members between which it extends, and the vane elements are all adapted to extend from the inlet end of the scoop means 38 to the outlet end thereof. More important, however, each vane element in configuration remains a plane in extending between the inlet and outlet end of the scoop means 38 and is also inclined or angled with respect to the two scoop member between which it extends. The configuration \Of the vane elements together with the positioning thereof thus define a plurality of spiral flow passages which create a spiral air flow from the outlet end of the scoop means defined by the end walls '76, 78, 80 and 82.

It will also be noted that the vane'elements between successive scoop members are alternately angled or inclined in opposite directions, as for example, vane elements '60 and 6 4 are inclined in one direction and vane elements 62 and 66 are inclined in the oppositedirection. This alternately inclined arrangement of the vane elements in eifect divides the spaces between the scoop members into a plurality of alternately and reversely spiralled oom partments which become progressively smaller in area or cross-section as the vane elements approach the outlet ends of the scoop members and which serve to discharge air into the combustion chamber in alternate counterrotating streams, the direction of flow of the counterrotating streams being shown by the arrows in Fig. 4. The alternately inclined arrangement of the vanes will insure that the counter-rotating streams of air are injected into the combustion chamber in a direction substantially tangential to the exit diameter of each of the scoop members and with the air being discharged from the innermost scoop member in a direction substantially tangential to the exit diameter of the fuel nozzle 42. Furthermore, it can readily be seen that the progressively decreasing area or cross-section of each compartment formed by the vane elements will produce a nozzle ef- "fec and thereby increase the velocity of the air as it passes through the scoop means 38.

The operation of the present invention can best be explained by again referring to Fig. 1. Air under pressure from any suitable source (not shown) is supplied to the inlet conduits 30-30 in housing 10 from where it passes into jacket 26 and then i captured by the scoop means 38. Fuel under pressure from a suitable source (not shown) will be simultaneously supplied to the nozzle 42 by conduit 50 and will pass through orifice 44 into the combustion chamber in a diverging flow pattern, the bevelled surface 48 defining the exit diameter of the orifice contributing in part to the creation of the diverging flow pattern. The air captured by the inlet end of the scoop means 38 will pass through the scoop means wherein it will be accelerated and discharged into the combustion chamber in four counter-rotating streams, the counterrotating air streams entering the combustion chamber in the region adjacent nozzle 42 with one of the streams entering in a direction substantially tangential to the exit diameter of the nozzle.

Due to the stepped construction or the progressively increasing diameters of the scoop members at the outlet end of the scoop means 38, the counter-rotating air streams will enter the combustion chamber in four sub- Is'tantially concentric rings or the like which are Spaced a predetermined distance apart along the axis of the combustion chamber to thereby create a highly turbulent and divergent vortex flow pattern of air therein. This divergent vortex flow pattern will of course coincide substantially with the divergent flow pattern of the fuel emerging from nozzle 42 and thereby insure a thorough mixing of the fuel and air that enters the combustion chamber. Furthermore, it will be appreciated that the frusto-conical portion 34 of the combustion chamber will insure a continuance of the divergent vortex flow pattern induced by the air inlet construction and will therefore serve to further enhance the thorough mixing of the fuel and air.

Performance tests conducted on combustion units utilizing the present invention have demonstrated a marked increase in combustion efiiciency due to the better mixing of fuel and air. This increase in combustion efliciency was found to be especially noticeable at lean mixtures. These performance tests also indicated that the introduction of air into a combustion chamber in counter-rotating streams resulted in only a small reduction in the vortex strength of the vortex flow pattern, the vortex strength being especially important in that it provides the energy source in the combustion chamber to establish recirculation and thereby insure the required combustion stability.

The stepped construction of the outlet end of the scoop means 38 of the present invention has been found to be most advantageous in that it contributes to the formation of a more nearly ideal point source for the vortex flow pattern in the combustion chamber 12. The reduction of the vortex pattern as close as possible to a single point source is especially desirable inasmuch as it is well known in principle that the more nearly an actual vortex source approaches a point, the more nearly it approaches the theoretical limit or ideal. Another advantage inherent in the present invention has been found to reside in the introduction of the air into the combustion chamber 12 in a direction substantially tangential to the exit diameter of fuel nozzle 42. Performance tests have indicated that air introduced in this fashion will result in a minimum of frontal area of the fuel nozzle 42 exposed to carbon build-up, the air thereby providing a shield for the frontal area of the nozzle.

While the present invention has been illustrated and herein described in connection with a scoop means comprised of four individual scoop members, it will be readily apparent to those skilled in the art that the scoop means could be modified to include a greater or lesser number of scoop members. The selection of any given number of scoop members is strictly a matter of choice and will be determined for the most part by the number of counterrotating air streams that are needed in any given environmental application. On the other hand, if it is not desirable to inject air into a combustion chamber in counterrotating streams in a given environment application, it will also be readily apparent to those skilled in the art that the scoop means could be constructed to include only two scoop members. a 7

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specificallydescribed,

What is claimed is:

1. In combination in a gas turbine engineor the like, a housing having a substantially frusto-conical shaped end defining a combustion chamber provided with a substantially frusto-conical shaped. inlet, an. air inlet means carried by said housing on the frusto-conical shaped end thereof for introducing air into the frusto-conical shaped inlet of said combustion chamber in a divergent vertex flow pattern, and nozzle means carried by said air inlet means for injecting fuel into the substantially frusto-conical shaped inlet of said combustion chamberin a-divergent flow path, said air inlet means being comprised of a p urality of nested bowl-shaped members having inlet and outlet ends, each of said nested, bowl-shaped members being spaced a predetermined distance apart and held in assembled engagement by a plurality of vane elements carried by and positioned therebetween with the innermost bowl-shaped member carrying a plurality of vane elements on the inner periphery thereof, said outlet ends of each of said nested, bowl-shaped members being progressively increased in diameter with the outlet end of the outermost of said bowl-shaped members being rigidly connected to the substantially frusto-conical shaped end of said housing, said nozzle means being rigidly connected to the plurality of vane elements carried on the inner periphery of said innermost bowl-shaped member with the outer peripheral surface of said nozzle means thereby functioning as another nested, bowl-shaped member, said vane elements extending between said inlet and outlet ends of said nested bowl-shaped members and being alternately inclined in opposite directions to thereby divide the spaces between said bowl-shaped members and the outer peripheral surface of said nozzle means into a plurality of alternately and reversely spiralled compartments having progressively smaller cross-sections as the vane elements approach the outlet ends of said bowl-shaped members, the progressively increasing diameters of the outlet ends of a plurality of said bowl-shaped members together with said alternately and reversely spiralled compartments formed by said vane elements being operable to discharge air into said frusto-conical shaped inlet of said combustion chamber in a region contiguous to said nozzle means in a plurality of counter-rotating, substantially circular streams spaced at predetermined distance apart and having progressively increasing diameters, said plurality of counterrotating, substantially circular air streams producing a diverging vortex flow pattern of fuel and air in the frustoconical shaped inlet of said combustion chamber.

2. In the combination set forth in claim 1 wherein the substantially circular stream of air discharged from the compartments formed by the vanes between the inner peripheral surface of the innermost bowl-shaped member and the outer peripheral surface of said nozzle means is discharged in a direction tangential to the exit diameter of said nozzle means whereby only a minimum of frontal area on said nozzle means is exposed to combustion and carbon build-up.

FOREIGN PATENTS Germany May 30, 1923 

